DIRECT OBSERVATION OF THIACARBOCYANINE J-AGGREGATES ADSORBED ON AGBR EMULSION CRYSTALS, USING HIGH-RESOLUTION SCANNING ELECTRON-MICROSCOPY

-sulfapropyl-5,5'-dichloro-9-ethylthiacarbocyanine dye J-aggregates ad sorbed on AgBr microcrystals grown in gelatin were imaged in a high-re solution scanning electron microscope when the incident beam energy wa s as low as 700 eV. At this voltage, the resolution of the microscope was 3 nm. High-resolution observation could be made at room temperatur e without irradiation damage. Specimen cooling by liquid N-2 made the image flat through accumulation of electronic charges on the specimen surface caused by low electron conductivity at low temperature. The J- aggregates aligned linearly along [210] directions on the (100) surfac e of AgBr as if they were one rod-like aggregate. The rod-like aggrega tes were frequently found to form clusters aligned parallel to each ot her. The aggregates sometimes built up a terrace with many rodlike agg regates to almost cover the surface. The edge of the terrace was clear , and no aggregates seemed to adsorb on the other side of the step. Th ese superstructures of J-agaegates caused heterogeneous distribution o f adsorption on the crystal. surface. Cathodoluminescence observation confirmed these results.